Order creation: Search Customers

[iamgabrielma]

Ref: pe5pgL-9t-p2

For parity with Android, we want to implement a "Search and Pick" functionality, for merchants to choose an existing customer when creating, or editing an order. Selecting this customer should auto-fill the Order details.

https://user-images.githubusercontent.com/3903757/174346481-5532091b-28e1-4c14-8107-05300aab04bf.mp4

Initial list of tasks:

• [x] Feature flag https://github.com/woocommerce/woocommerce-ios/pull/7743
• [ ] Update Network layer: https://github.com/woocommerce/woocommerce-ios/pull/7746
• [ ] Update Network layer for GET /wc-analytics/customers?search= (Why? pe5pgL-3r-p2)
• [ ] Add GenerateFakeable, and Copiable conformance
• [ ] Update Storage layer
• [ ] Update Yosemite layer
• [ ] Add "Search Customers" view. Implement SearchUICommand (needs model)
• [ ] Analytics: order_creation_customer_added, order_creation_customer_search
• [ ] Fetch Customer data
• [ ] Auto-fill